Micro four thirds vs. full frame

[paddler4]

As some of you know, I bought an OM-1 Mark II to save weight relative to my previous camera, a full frame Canon (R6 Mark II). It was a concession to age. Since then, I have been trying the OM-1 for various types of photography to see how the two compare, although I haven't done A/B comparisons of the same shot.

So far, my conclusion is that the OM-1 is fine for most purposes and superior for a few, but there is one so far for which is it clearly not as good: night photography. The R6 provides better shadows and has more dynamic range (Urban night photography is one of the few genres where that actually matters, given the large DR of modern sensors.) When set to auto, the R6 doesn't use long-exposure (black frame subtraction) for most urban night photography images. The OM-1 applies it to captures of even just a few seconds, although I don't know whether it's needed at those shutter speeds. Shooting at base ISO, the R6 images are so clean, even under those conditions, that I almost never apply any other noise reduction at all. If I pixel peep, the OM-1 images are improved by running Adobe's AI-based denoise immediately after importing the raw file.

Still, the OM-1 is capable of producing very good night images. Here's one I took recently. It's ISO 400, 15 seconds, f/9.5. I don't normally boost ISO at all for shots like this, but 15 seconds was about as long as I could get without the occasional car ruining the shot.

 

[Wilt]

A larger format digital will generally have better signal-to-noise (lower noise) than a smaller sensor, given the same pixel count. The pixel/sensel with larger area will be able to capture more photons in the same amount of time, so there is more signal (for the same level of background circuit noise) to overcome the noise. So the smaller sensor has to apply more noise processing to get the same level of freedom from noise. The real question is 'what is good enough for YOU?' !

At the same time, the smaller format will generally have less shallow DOF, using the same shooting aperture for the same angle of view. Some folks demand really shallow DOF for certain shooting circumstances, which might not be achievable when shooting with smaller format. Again, the real question is 'what is good enough for YOU?'

At the same time, the larger format is generally heavier and bulkier to carry, for an equivalent kit. Does that matter to you?

Photogtraphy is a whole bunch of tradeoffs to weigh against each other, and what matters the most to one is different from what matters the most to another, and may well change depending upon shootiing circumstance.

 

[paddler4]

Sorry, I wasn't clear in my post. I know those tradeoffs, and I was writing without thinking about the many people who don't. Egocentric of me.

I bought the OM-1 primarily because of weight. Since getting it, I have been trying it in a variety of different circumstances to see when the tradeoffs matter in practice, given what I shoot and how I present--in prints, usually up to 13 x 19 inches (A3+), but sometimes 17 x 22 (A2). I still have my R6 II and several lenses and have been trying to decide whether it's worth keeping them.

Apart from the obvious benefit of much lower weight, which has practical implications for me most of the time, the difference hasn't mattered very much in most of what I have tried so far. I really doubt that anyone would actually notice which print came from which camera most of the time. It makes even less difference online, of course, because of the lower resolution of computer monitors.

However, there are a few cases where that's not a clear conclusion. This is one of them. I haven't used my R6 II once since buying the OM-1, but I think I may use it for night photography, at least when I don't need to hike a long distance. I'm going to be showing an 11 x 14 print of this image to some other photographers tonight to get their impressions.

Concerning the other tradeoffs: the deeper DOF is mostly an advantage for me, not a disadvantage, given what I shoot. For field macro, the smaller sensor of the OM-1 with its higher pixel density is in general a big advantage, but what comes with it is shorter focal lengths for a given angle of view, which is a disadvantage because of shorter minimum working distance (scares off bugs). There are camera-specific tradeoff as well; for example, the OM-1 has vastly better computational photography capabilities, and the larger size of the R6 makes it more comfortable in the hand for me.

 

[Wilt]

Macro work brings its own set of uniqueness.
Computation of DOF, using FF and 50mm FL on 50mm extension vs. OM-1 using 30mm FL on 30mm extension, to result in 1:1 magnification from both formats yet actually yields a smaller DOF on the smaller format!

0.2m (FF) vs. 0.12m (MFT)​

https://www.kielia.de/photography/calculator/

 

[paddler4]

Macro work brings its own set of uniqueness.
Computation of DOF, using FF and 50mm FL on 50mm extension vs. OM-1 using 30mm FL on 30mm extension, to result in 1:1 magnification from both formats yet actually yields a smaller DOF on the smaller format!
0.2m (FF) vs. 0.12m (MFT)

True, there are a number of reasons why the simple lens formula doesn't strictly apply at macro distances, but the basic principles apply even though the numbers are off. However, the question of how sensor size affects DOF doesn't have a simple answer. It depends on whether one is maintaining the same angle of view by using a shorter focal length, what the pixel size and hence the circle of confusion is, and whether one is referencing image size independent of frame size or similar framing, among other things. Here is a slide from Marc Levoy's famous class at Stanford for one of those circumstances:

The best summary I know of the effects of sensor size on DOF under a variety of circumstances is an old post by Bob Atkins. He specifically wrote about FF vs. APS-C, but the principles apply generally.

https://bobatkins.com/photography/technical/digitaldof.html